Many lines of evidence point to the cerebellar cortex as having a parasagittal organization. This evidence includes anatomical tracing studies, electrophysiological single unit studies, histochemical and immunohistochemical analyses of the cerebellum. Even though these various methodologies have been successful in demonstrating parasagittal organization of one form or another, there have been relatively few attempts to compare, collate, and synthesize the data from these different methodologies. It is absolutely essential to attack this problem if we are ever to determine the true nature of cerebellar parasagittal organization and its functional significance. We have been using anatomical tracing techniques to study the parasagittal organization of the cerebellum in the rat and mouse. By using these data as a starting point we propose to compare and contrast, in a detailed and thorough way the parasagittal organizational schemes which result when different methodological approaches are applied to the same species. This represents a logical and important extension of the work we have been doing on afferent organization to the cerebellum. Toward this end we plan to carry out the following experiments. (1) Compare and analyze, in the same animal, the immunohistochemical staining pattern of Purkinje cells obtained with the monoclonal antibody Q113 and Q155, to the pattern of climbing fiber afferents to the cerebellum as demonstrated with WGA-HRP anterograde tracing techniques. (2) Carry out a detailed analysis of one lobule of the cerebellum (lobule VIII and the copula pyramidis) with regard to the pattern of its climbing fiber and mossy fiber inputs as studied with WGA-HRP retrograde tracing techniques and the immunohistochemical staining pattern of this lobule with mab Q113. (3) Conduct a similar comparative analysis with 5' nucleotidase histochemical staining patterns and the pattern of afferent input. (4) Determine the dependency, if any, of these staining patterns (5' nucleotidase, mab Q113, and/or Q155) on the integrity of the olivocerebellar projection by making unilateral chemical lesions of the inferior olivary complex.